7. Sensory Processing 1 Flashcards
(93 cards)
1
Q
The retina is the ___ ___ of vision
A
Sensory organ
2
Q
What are the 3 main layers of the retina?
A
Photoreceptor layer, intermediate layer and the ganglion cell layer
3
Q
What is found in the photoreceptor layer?
A
Rods and cones
4
Q
What is found in the intermediate layer?
A
Bipolar, horizontal and amacrine cells
5
Q
What is found in the ganglion cell layer?
A
Retinal ganglion cells: midget & parasol
6
Q
What do rods and cones respond to?
A
Light intensity
7
Q
In the darkness what do rods and cones release?
A
A neurotransmitter (glutamate)
8
Q
Light is absorbed by what in rods and cones?
A
A pigment
9
Q
Name the pigments in rods and cones
A
Rhodopsin
Cone opsin
10
Q
The change in shape in the shape of photopigment triggers what?
A
A G-protein cascade that reduces glutamate release
11
Q
What do bipolar cells do?
A
They transfer information from rods and cones to retinal ganglion cells
12
Q
The intermediate layer transforms light information into what?
A
Contrast information
13
Q
What are the two types of bipolar cells?
A
On and off
14
Q
On bipolar cells are ___ by input
A
Inhibited
15
Q
Off bipolar cells are ___ by input
A
Excited
16
Q
What are the two types of retinal ganglion cells?
A
Parasol and midget
17
Q
Describe parasol ganglion cells
A
Large dendritic trees
Combine inputs from many bipolar cells
18
Q
Describe the midget ganglion cells
A
Combine inputs from few bipolar cells
Dendritic trees larger in periphery for both
19
Q
What is the term which describes how photoreceptors translate light into neural signals for light intensity?
A
Signal transduction
20
Q
What type of cells convert signals for light intensity into signals for contrast?
A
Bipolar and ganglion cells
21
Q
Define visual receptive fields
A
The region of sensory space that evokes a response in a neuron
22
Q
RFs have a ___ and ___
A
Position and size
23
Q
What are the two types of sub-region in RFs?
A
Excitatory and inhibitory
24
Q
On RFs respond to an ___ in light intensity
A
Increase
25
Off RFs respond to a ___ in light intensity
Decrease
26
Retinal ganglion cells RFs mostly have what type of organisation?
Centre-surround organisation
27
Photoreceptors respond to what?
Light intensity
28
Retinal ganglion cells RFs code for what?
1. Differences in light and dark over time (flicker)
2. Differences in light and dark over space (contrast)
3. Differences in colour
29
What shape are retinal ganglion cell RFs?
Circular
30
How many layers does the LGN consist of?
Six
31
The layers in the LGN differ in terms of what things?
The kind of cells they contain
What type of visual input they receive
Which eye they receive input from
32
What are the two main visual pathways in the LGN?
Magnocellular (M) pathway
| Parvovellular (P) pathway
33
Which layers are the M pathway?
Inner two layers (1 & 2)
34
Where does the M pathway receive input from?
Parasol ganglion cells
35
Which layers are the P pathways?
The outer four (3, 4, 5, 6)
36
Where does the P pathway receive input from?
Midget ganglion cells
37
Receptive fields in LGN are similar to those of what?
The retinal ganglion cells
38
What are the 5 functions of the LGN?
1. Relay station between eye and brain
2. Response properties similar to retinal ganglion cells
3. Receives massive feedback from the cortex
4. First site of attentional gating/enhancement
5. Sleep-related gating of sensory input to cortex
39
V1 is also known as what?
The Striate cortex
40
Most LGN neurons project to where?
V1
41
V1 consists of how many layers?
Six layers
42
P pathway projects to where in V1?
VCB
43
The P pathway splits into 2 new pathways in V1, what are they and what do they do?
P-B pathway: colour (blobs)
| P-I pathway: orientation (inter blobs)
44
Describe how M pathway projects into V1
1. Project to layer 4C to 4B
2. Cells in layer 4B are sensitive to movement
3. Some are binocular and disparity/depth sensitive
45
Most cells in V1 are ____ (respond to stimulation in either eye)
Binocular
46
Cells in layer 4 that receive input from LGN are ___ (respond to only one eye)
Monocular
47
Define ocular dominance
Most cells respond better to stimulation from one eye or the other
48
What are ocular dominance columns?
Cells preferring each are are clustered into ~1mm thick slabs
49
What are the 5 functions of V1?
1. Topographic organisation
2. Contains a map of the visual field
3. Detailed maps of orientation, colour, spatial scale, motion direction and 3D depth
4. Projects to most higher visual areas in cortex
50
What 4 things does V1 compute?
1. Orientation
2. Spatial frequency
3. Motion
4. Colour
5. Depth
51
V1 cells respond best to a limited range of what?
Temporal frequency (flicker rate; how quickly stimuli change over time)
52
Cells in M pathway respond better to ___ flicker
Fast
53
Cells in the P pathway respond best to ___ flicker
Slower
54
Neurons in V1 project to higher visual cortical areas such as:
V2, 3, 3A, 4, 5...
55
What do the different higher visual cortical areas respond to?
V5: Motion
V4: Shape and colour
V3/3A: Motion boundaries and textures
56
Area V2 is divided into multiple what?
Stripes
57
Describe the features of the thick stripes (M pathway) from V2
Sensitive to orientation and movement
| Sensitive to disparity
58
Describe the features of the thin stripes (P pathway) from V2
Sensitive to colour
| Not orientation-selective
59
Describe the features of the inner-stripes (P pathway) of V2
Orientation-selective
| Not direction-selective
60
Describe the 3 features of V4
1. The P pathway projects to V4
2. Damage to human V4 impairs colour perception
3. Involved in shape discrimination
61
The M pathways projects to which visual areas?
V3/3A and V5
62
Describe the features of V3/V3A
Selective for orientation
| Respond to motion boundaries
63
Describe the features of V5 (MT)
Selective for motion, direction and speed
| Process information on motion and stereoscopic depth
64
What does the frequency refer to?
The speed of vibrations
65
Amplitude refers to what?
The size of the vibrations
66
A sound at a single frequency is a pure tone, what type of wave does a pure tone look like?
A sine wave
67
The auditory system works by taking apart what into what?
Sounds into their component frequencies and 'measuring' the amplitude of each component
68
Humans can detect sounds between what measurements of Hz?
20-20,000 Hz
69
How is the anatomy of the ear divided?
Into outer, middle and inner
70
Auditory sensory neurons are located in which area of the ear?
The inner ear
71
What are the two main functions of the outer ear?
1. Amplifying sounds around 3kHz
2. To help determining the direction of a sound (by allowing through more high frequencies from a high than a low sound source)
72
What is the function of the middle ear?
To amplify sounds so they can pass from air to water
73
What are the two mechanisms of the middle ear?
The eardrum and the ear bones
74
Describe the eardrum (tympanic membrane)
Much larger than the oval window, giving a proportional amplification
75
Describe what the ear bones (ossicles) do?
Act as levers, magnifying the force of vibrations
76
The inner ear consists of the cochlea and the semicircular canals, describe the features of these
Semicircular canals are part of the vestibular system
| The cochlea is a hollow spiral tube
77
The cochlea contains what organ?
The Organ of Corti - the sensory organ of hearing
78
The organ of corti runs along the length of what and sits where?
The length of the cochlea
| It sits between two liquid-filled tubes of the cochlea
79
Hair cells are the ___ ___ of hearing
Sensory neurons
80
What are the two types of hair cells?
Outer hair cells and inner hair cells
81
IHCs and OHCs form two sets of rows which run along the length of what?
The cochlea
82
Describe the 3 stages of how hair cells respond to sound
1. Sound vibrations cause the basilar membrane to vibrate
2. This causes a 'shearing' motion of the BM relative to the tectorial membrane
3. This causes hair cells that sit between the BM and TM to bend back and forth
83
Describe the signal transduction by hair cells
- Bending of the 'hair' of hair cells pulls filaments connecting sterocilia
- These filaments (tip links) are believed to connect mechanically to ion channels in the hair cells, opening them
- This causes the hair cells to depolarise and fire APs
84
Hair cells respond ___ ___
Very fast
85
Allows hair cells to fire synchrony with sound vibrations up to ___ kHz
3
86
What are the outer hair cells for?
They receive neural input from the auditory nerve
In response to stimulation, outer hair cells can contract and modify stiffness of basilar membrane - allowing fine tuning of sound sensitivity
87
What is the purpose of cochlear implants?
To directly stimulate the auditory nerve - to mimic the function of hair cells
88
Axons from the inner hair cells join to form what?
The auditory nerve
89
The auditory nerve connects the cochlea with the ____ in the brainstem
Olive
90
What is the olive involved in?
Sound localisation
91
Auditory information passes through the MGN into the ___ and the ____
Thalamus and the auditory cortex
92
Describe the two mechanisms that localise sounds
Time difference between the ears
Processed in the medial superior olive
Intensity differences between the ears
Processed in the lateral superior olive
93
Where is sound information processed?
In the primary auditory cortex which is located in the superior temporal lobe
